Apparatus for relaxing yarns

ABSTRACT

Apparatus for relaxing yarns comprising a fluid device for tensioning and forwarding the yarn to a hot relaxation zone wherein tension is caused to fall.

United States Patent Elliott et al.

[54] APPARATUS FOR RELAXING YARNS [72] Inventors: David Robert Elliott;John Michael Greenway, both of Harrogate, England [73] Assignee:Imperial Chemical Industries Limited,

London, England [22] Filed: Dec. 31,1969

[21] Appl. No.1 889,518

[ 1 Feb.29, 1972 3,346,932 10/1967 Cheape ..28/l.4 X 3,435,497 4/1969Stanley ...28/72.l4 3,439,391 4/1969 De Vore et al ..28/62 X FOREIGNPATENTS OR APPLICATIONS 6,708,743 7/1968 Netherlands ..28/l 74 PrimaryExaminer-Louis K. Rimrodt Attorney-Cushman. Darby 8: Cushman [5 7]ABSTRACT Apparatus for relaxing yarns comprising a fluid device fortensioning and forwarding the yarn to a hot relaxation zone whereintension is caused to fall.

8 Claims, 2 Drawing Figures Patented Feb. 29, 1972 3,644,968

2 Sheets-Shoot 1 Patented Feb. 29, 1972 3,644,968

2 Shuts-Shoot 2 Fig.2

APPARATUS FOR RELAXING YARNS This invention relates to the treatment ofyarns and in particular to a device for the relaxation of yarns composedof thermoplastic polymeric material.

In the production of artificial or synthetic thermoplastic continuousfilamentary yarns they are subjected to a drawing or stretching processunder tension, following which it is usually required to relax the yarnpartially or completely either to produce the desired physicalproperties, such as a reduced shrinkage propensity in the processed yarnor to produce some other effect, such as bulking or crimping of thefilaments comprising the yarn when these have an inherent tendency toretract into a crimped form under low tension, optionally assisted byheat.

Hitherto such relaxation, has been carried out either by a batchprocess, wherein the yarn is temporarily collected in some form ofpackage which allows a degree of contraction to take place or bycontinuously subjecting the running yarn to treatment with a hot fluidin some form of jet device. These methods, in particular the latter one,suffer from the disadvantage that the yam properties produce fall shortof the ideal particularly for materials subject to crystallization underthe influence of heat.

According to the present invention we provide apparatus for relaxing arunning yarn composed of thermoplastic polymeric material, comprising ayarn supply means, a fluid tensioning device, means for introducing agaseous fluid under pressure to the fluid tensioning device and aheating zone incorporating means for reducing the yarn tension duringits passage through the heating zone.

Yarn may be supplied to a fluid tensioning device in the presentinvention direct from the draw roll of a drawing machine or the drawnyarn may be temporarily packaged under tension from which package it issupplied to the fluid tensioning device by way of a tension gate or feedroll/nip roll combination. The former continuous method of operation ispreferred.

A fluid tensioning device for use in the invention comprises anaspirator or ejector jet which may have any of several forms. One suchform comprises a yarn entry passageway of narrow bore into which yarn isdrawn by the suction developed therein by entry into the passageway ofan unheated or a heated gaseous fluid under pressure downstream of thepoint of entry of the yarn, said fluid proceeding through the passagewayin a generally downstream direction. A fluid pressure is used such as toprovide the required tension to draw the yarn from the supply means intothe yarn passageway and forward it to a heating zone.

In another form of fluid tensioning device the yarn entry tube orpassageway is quite short and its lower end is surrounded by the openend of a slightly larger tube. The junction of the two tubes is enclosedin a chamber to which gaseous fluid under pressure is supplied. Thefluid enters the larger tube through the space between the two tubes andin passing through the larger tube induces a reduced pressure in theyarn passageway which draws a yam thereinto tensioning and forwarding itthrough the larger tube to the heating zone. Gaseous fluid supplied tothe chamber surrounding the junction of the two tubes, may be unheatedor heated and in the latter case the fluid may be supplied at a pressuresufficient to draw enough unheated ambient air into the yarn tube withthe yarn so that the yarn, while under tension before passing into theheating zone where tension is reduced, is not subject to heat. When heatcrystallizable yarns such as polyethylene terephthalate are treated itis preferred to operate apparatus according the the invention eitherwith unheated air or with heated air as in the latter described way.

A preferred form of heating zone according to this invention comprisesan enclosure directly attached to the yarn exit passageway of the fluidtensioning device and of larger cross section than said passageway intowhich the yarn is fed by means of a rotating tube having its exitdirected radially or tangentially away from the axis of the enclosure.The enclosure is heated by suitable means, as for example, a heatedvapor jacket or electrical heaters mounted externally. By this meansthere is a drop in pressure and velocity of the fluid as it expands intothe enclosure allowing the yarn to relax and fall through the heatedatmosphere within the enclosure in a substantially tensionless state. inoperating apparatus of this type to the best advantage it is preferredto cause the yarn to leave the rotating tube at a sufficient velocity tobe carried across the gap between the end of the tube and a wall of theheated enclosure and to strike the wall thereof preferably tangentiallybefore continuing to fall through the heated atmosphere. This gap may bequite small, for example 3-5 mm. In this way the yarn takes a morestable and even, helical path through the heating zone and therelaxation process operates more effectively. The part of an enclosurewall contacted by the yarn should be smooth and free from irregularitieswhich could snag the yarn and may be specially treated to produce a lowfriction, as for example covered with a layer of polytetrafluorethylene.Alternative to the rotating yarn exit passageway a stationary tubedirecting the yarn tangentially toward a wall of the enclosure may beused or a tube which oscillates to and fro causing the yarn to assume azigzag path through the heating zone.

Apparatus as hereinbefore described wherein the relaxing yarn is causedto follow a sinuous path through a heated enclosure has an especialadvantage in that it allows a yarn relaxation treatment to be carriedout continuously without interrupting the movement and at the same timeto allow a wide variation of treatment time without altering theenclosure length by control of the length of the yarn path within theheated enclosure. Such control is effected by, for example, alterationof the rotational or oscillatory speed or the radius of rotation oramplitude of oscillation of the yarn delivery tube or variation of theratio of the speed of supply of yarn to the relax zone to the speed ofwithdrawal from the relax zone. The last mentioned ratio is hereinreferred to as the relax ratio.

In an alternative form of heating zone yarn issuing from a fluidtensioning device enters an externally heated passageway of either auniform larger cross section or of a steadily increasing cross section.In the latter form a taper of not greater than 10 is preferred. lnapparatus of these forms the velocity and pressure of the entering fluidcarrying a yarn either rapidly or steadily decrease allowing yarntension to decay and relaxation under the influence of heat. The lengthof the heating zone is selected to allow the required amount ofrelaxation which is also influenced by the heating zone temperature.Threading up a fluid tensioning device with a running yarn which ishandled by a temporary collecting means as for example a suction gun,may be facilitated by providing a narrow longitudinal slot in thetensioning device and the relax zone.

Air is the most convenient fluid for use in this invention but othergases not having any harmful effect on thermoplastic polymericsubstances may be used.

Alternatively to externally heating the heating zone a slow coorcounter-current flow of hot gas may be used instead provided care istaken to ensure that the relaxing yarn is not disturbed by the hot gas.In this case steam particularly dry steam may be used as the gas.

Yarn emerging from the heating zone is collected in any way which doesnot allow collecting tension to run back to the relaxation zone. Forexample a pair of rolls pressed into close contact with each other andpreferably with one surface covered by a resilient material (that is aroll/nip roll combination) may be used to takeup the yarn emerging fromthe relax zone and to forward it to any suitable yarn packagingapparatus. By this means the amount of relaxation occurring may becontrolled by adjusting the relative speeds of this roll combination andthat of the supply of yarn to the relax process.

The invention is illustrated in the attached drawings which show variousforms of apparatus for carrying out the relaxation process.

FIG. 1 illustrates in section relaxation apparatus of the preferred formwherein a counter current flow of hot air is used to effect relaxationof yarn fed in by means of a rotating tube;

FIG. 2 illustrates in section a relaxation apparatus wherein relaxationis effected in a uniformly divergent enclosure.

Referring to FIG. 1 a yarn tensioning device comprises a yarn entry tube2 of narrow bore the open lower end of which is spaced a small distancefrom an exit passage 3 of a surrounding enclosure 4 to which fluid underpressure is supplied at 5. Exit passage 3 is joined by a swivel coupling6 to a rotatable tube 7 bent at its lower end towards a wall of anenclosing vessel 8 of very much increased cross section. A pulley 15mounted at the upper end of tube 7 allows the tube to be rotated bysuitable driving means (not shown). Vessel 8 is open at its lower endand closed at its upper end except for an opening through which the tube7 extends and two small slots 9 near the point of entry of the rotatabletube 7. Mounted around the lower end of vessel 8 is a hollow ring 10,the internal wall 11 of which is of sintered metal or other porousmaterial of sufficient strength to which a conduit 12 for the supply ofhot fluid is attached. Situated some distance below the open end ofvessel 8 is a takeoff roll 13 against which a rubber covered nip roll 14is firmly pressed.

ln operation a yarn 1 is drawn from a supply means (not shown) into theyarn entry tube 2 by the suction generated therein by passage of thecompressed fluid from passing into exit passage 3 through the smallclearance between tube 2 and passage 3. The yarn forwarded by the fluidthrough the rotating tube 7 exits therefrom and impinges against thewall of vessel 8 falling in substantially uniform helical coils throughthe atmosphere of heated fluid in the enclosure 8 supplied from ring ina steady upward current through the porous wall 1 1. The upward velocityof air is controlled at a low value by the pressure within ring 10 andthe size of slots 9 which may be of adjustable opening. The relaxed yarnissuing from enclosure 8 may be allowed to cool by natural convectionwhile passing to rolls 13/14 or by a forced current of cooling airapplied after rolls 13/14, preferably in a manner which does not allowtension to develop in the yarn while it is still warm or hot. Therelaxed yarn passes through the nip between rolls 13 and 14 to aconventional winding means (not shown) the winding tension being stoppedat the nip.

Referring now to FIG. 2 a cylindrical casing 15 carries the parts of theapparatus in easily demountable form. A cap 16 spigotted into the upperend of casing 15 and retained in place by screws 17 carriessymmetrically a number of holes 18 for entry of the working fluid. Ayarn entry tube 19 is inserted through a central hole in cap 16protruding some distance into the casing 15. Inside the casing 15 spaceda small distance from the lower side of cap 16 by a spacing ring 20 is adiffusing plate 21, of, for example, sintered metal, through a bush 22in which the exit end of the yarn tube 19 protrudes into a cavity formedat the upper end of a block 23 which carries the upper end of adivergent yarn passageway 24 in communication with cavity 30 and ispositioned within the casing 15 by means of a tubular spacer 25 retainedin the casing by screws 26. The lower and major part of passageway 24which protrudes from the lower end of casing 15, is supported bybrackets 27 attached to casing 15 and is surrounded by heating means(not shown). A small groove 23 in the top of block 23 allows a pressureor other measuring instrument to be at tached through a tapping 29 inthe casing 15.

in operation compressed fluid entering holes 18 passes through thediffusing plate 21 into cavity 30 and thence into passageway 24 therebyinducing a suction in tube 19 which draws in a yarn (not shown)tensioning it within the tube 19 and forwarding it through passage 24 ata reducing fluid velocity and under increasing relaxation conditions.The relaxed yarn leaving the lower end of passage 24 may be taken up andcollected into a package as in the foregoing description.

Yarn composed of filaments or fibers of any thermoplastic polymericmaterial or materials may be relaxed in apparatus accordin to thepresent invention, as for example polyesters, polyami es, polyolefinesor copolymers within or between the invention when a good bulk andcrimping effect is ob tained in a continuous process.

What we claim is:

1. Apparatus for relaxing a running yarn composed of thermoplasticpolymeric material, comprising a yarn supply means, a fluid tensioningdevice, means for introducing a gaseous fluid under pressure to thefluid tensioning device and a heating zone incorporating means forreducing the yarn tension during its passage through the heating zone,said heating zone and means for reducing yarn tension comprising anenclosure of larger cross section than the yarn passageway which isheated externally or through which a current of heated fluid is passedand a rotatable or oscillatable passageway connected to the yarnpassageway, which directs the yarn into the enclosure in a sinuous orzigzag path.

2. Apparatus according to claim 1 wherein the rotatable passagewaydirects the yarn toward a wall of the enclosure.

3. Apparatus according to claim 2 wherein the part of the enclosure wallagainst which the yarn is directed is treated to produce a low friction.

4. Apparatus according to claim 3 wherein the part of the enclosure wallis covered with polytetrafluoroethylene.

5. Apparatus according to claim 1 wherein the current of heated fluidpasses through the enclosure in the same or opposite direction to thatof yarn movement through the enclosure.

6. Apparatus according to claim 1 wherein the fluid tensioning devicecomprises a yarn passageway and means permitting entry thereinto offluid under pressure and for directing it in the desired direction ofyarn movement.

7. Apparatus according to claim 6 wherein the fluid entry meanscomprises a passageway connected to a supply of fluid under pressureopening into the yarn passageway.

8. Apparatus according to claim 6 wherein the fluid entry meanscomprises a second passageway positioned below the yarn passageway,substantially coaxial therewith and of larger bore into which the yarnpassageway enters and which forms a continuation thereof, the junctionof the two passageways being connected to a supply of fluid underpressure.

1. Apparatus for relaxing a running yarn composed of thermoplasticpolymeric material, comprising a yarn supply means, a fluid tensioningdevice, means for introducing a gaseous fluid under pressure to thefluid tensioning device and a heating zone incorporating means forreducing the yarn tension during its passage through the heating zone,said heating zone and means for reducing yarn tension comprising anenclosure of larger cross section than the yarn passageway which isheated externally or through which a current of heated fluid is passedand a rotatable or oscillatable passageway connected to the yarnpassageway, which directs the yarn into the enclosure in a sinuous orzigzag path.
 2. Apparatus according to claim 1 wherein the rotatablepassageway directs the yarn toward a wall of the enclosure.
 3. Apparatusaccording to claim 2 wherein the part of the enclosure wall againstwhich the yarn is directed is treated to produce a low friction. 4.Apparatus according to claim 3 wherein the part of the enclosure wall iscovered with polytetrafluoroethylene.
 5. Apparatus according to claim 1wherein the current of heated fluid passes through the enclosure in thesame or opposite direction to that of yarn movement through theenclosure.
 6. Apparatus according to claim 1 wherein the fluidtensioning device comprises a yarn passageway and means permitting entrythereinto of fluid under pressure and for directing it in the desireddirection of yarn movement.
 7. Apparatus according to claim 6 whereinthe fluid entry means comprises a passageway connected to a supply offluid under pressure opening into the yarn passageway.
 8. Apparatusaccording to claim 6 wherein the fLuid entry means comprises a secondpassageway positioned below the yarn passageway, substantially coaxialtherewith and of larger bore into which the yarn passageway enters andwhich forms a continuation thereof, the junction of the two passagewaysbeing connected to a supply of fluid under pressure.